This application relates to welding technique that reduces cracking due to welding operations to close off the end of internal cores in turbine components.
Gas turbine engines are known and typically include a compressor which compresses air and delivers it into a combustion chamber. The air is mixed with fuel and combusted in the combustion chamber. Products of this combustion pass downstream over turbine rotors.
The rotors include a number of components, including removable blades, and seals which sit outwardly of the blades. The products of combustion can be extremely hot, and thus these components must be capable of withstanding high temperatures. One design feature to address the high temperature is to provide cooling air through internal passages in the blades and the seals.
To form the internal passages, lost cores are utilized. A lost core is typically a product shaped to mimic the shape of the cooling passage that is desired within the final turbine components. The turbine component is cast around the core product, and the core product is then removed in some manner, such as being leached, leaving the empty space for the cooling passage.
In one lost core technique, the cores are supported such that one end of the core is structurally mounted within a cast mold. As a machining step, that end of the core passage is closed off after the component has been cast. In the existing method, weld wire is manually extended into the passage, and welded to fill the passage outwardly toward the final outer face of the turbine component. The turbine component is then machined downwardly to a final face.
The above method applies a great deal of heat to the turbine component around the area of the weld wire. Cracking often results.